This is a Shannon Award providing partial support for the research projects that fall short of the assigned institute's funding range but are in the margin of excellence. The Shannon Award is intended to provide support to test the feasibility of the approach; develop further tests and refine research techniques; perform secondary analysis of available data sets; or conduct discrete projects that can demonstrate the PI's research capabilities or lend additional weight to an already meritorious application. The abstract below is taken from the original document submitted by the principal investigator. Despite the prevalent and often chronic use of muscle relaxants in critically ill patients requiring ventilatory support, little is known about the biochemical changes subsequent to such treatment. Clinical experience suggests that chronic muscle relaxant administration can result in long-term muscle weakness requiring prolonged rehabilitation. Since muscle relaxants block nicotinic acetylcholine receptor (nAChR) activity, a possible molecular basis for this long-term paralysis is chemical denervation of skeletal muscle by these agents. Because denervation results in dramatic changes in the transcriptional activity of nAChR subunit genes, we will develop and use a very sensitive method to quantitate subunit mRNAs: the RNase protection assay. Specifically, we will: 1) develop a quantitative assay initially in rat muscle. RNase protection will be used to measure mRNAs in skeletal muscle extracts encoding the five subunits (alpha, beta, gamma, delta, and epsilon) that comprise either fetal (gamma) or adult (epsilon) rat muscle-type nAChR; 2) determine changes in levels and type of nAChR subunit mRNAs expressed in muscle from rats administered muscle relaxants via indwelling infusion with respect to: a) time course for changes (i.e., epsilon to gamma); b) structural type of muscle relaxants used; and c) concomitant use of glucocorticoids; and 3) compare these changes to: a) changes in receptor density as determined by specific alpha-BTX binding; b) changes in muscle relaxant plasma concentration necessary to produce neuromuscular blockade. Using methodology developed in rats, we will then test the hypothesis that chronic muscle relaxant administration to patients in an intensive care unit (ICU) setting can result in a denervation-like syndrome. That is, we will: 1) adapt the RNase protection assay to measure mRNA encoding the five human muscle nAChR subunits in control human muscle specimens; 2) randomly assign ICU patients requiring muscle relaxants to facilitate mechanical ventilation to receive either vecuronium or atracurium. Autopsy muscle specimens from this pool of ICU patients will be examined for level and type of human nAChR subunit mRNAs expressed as determined by RNase protection assay and receptor density; 3) evaluate these results with respect to: a) type and total dose of muscle relaxant used; b) age and gender differences; c) concomitant steroid use; and d) underlying disease process. Given the potential complications to patients of prolonged paralysis, more research is warranted to determine proper use of muscle relaxants in the intensive care setting. The work described in this proposal will provide a molecular basis for guidelines in the administration of these drugs.